Over the next year a new project studying the effect of tumor endothelial cell interaction on vascular invasion, will be initiated. Quantitation of tumor cell collagenase gene expression will be used at first as a marker for invasive potential. Secreted factors that either inhibit or stimulate the tumor cell collagenase will be looked for in conditioned media from capillary, venous and arterial endothelial cells. The effect of attachment between endothelial and tumor cells on collagenase expression will be studied in co-cultures of the two cell types. Tumor cell collagenase expression in the co-cultures will be quantitated by using in situ hybridization technique, followed by positive identification of the endothelial cells through immunostaining for factor VIII antigen. If collagenase stimulating factors expressed by endothelial cells, either as secreted or cell surface proteins will be identified, we will proceed to isolate and purify such factors.